1. Field of the Invention
The present invention relates to a hand-held tool machine having a switchable mechanism.
2. Description of Related Art
From published German patent application document DE 10 2004 058 809 A1, a battery-powered screwdriver is known, which has an electrical drive motor which drives a tool holder for accommodating a tool via a multi-stage planetary gear, the tool holder being rotatably supported in the housing.
Such battery-powered screwdrivers are frequently equipped with a switchable planetary gear, which is able to be switched between a first gear ratio having a slow rotational speed and high torque, and a second gear ratio step having a higher rotational speed and lower torque. The switchover is achieved with the aid of a gear shifter in the form of a slider on the outside of the housing, which can be manually adjusted in the axial direction, thereby causing the displacement of an internal gear wheel between two switching positions. The internal gear wheel acts on a gear wheel of the planetary gear, which is coupled to the housing in a first switching position, and coupled to a planetary-gear carrier of the planetary gear in a second switching position.
In this context it should be noted that the locking of the internal gear wheel when a switch takes place between the gear ratios may be more difficult, in particular under load, due to differences in the rotational speeds. For this reason spring elements may be provided, which in response to the corresponding actuation of the gear shifter apply force to the internal gear wheel in order to bring it into the desired switching position, so that the internal gear wheel locks into the desired switching position only after the drive motor has been switched off and the internal gear wheel has been switched on again. However, the force of the spring elements must be adapted to the force of a further spring element, with whose aid the gear shifter is securely retained in its particular switching positions in order to prevent unintentional resetting of the gear shifter. On the other hand, the spring force acting on the gear shifter must not be excessive either in order to ensure an ergonomic actuation of the gear shifter.